1. Field of the Invention
This invention is generally related to digital communication systems and, more particularly, to a system and method for using error correction information to adjust receiver parameters in the improvement of information throughput.
2. Description of the Related Art
Digital signals are typically processed as a serial data stream and recovered using amplitude and timing parameters. Alternately stated, the amplitude of the digital signal must be monitored to detect the difference between a xe2x80x9c1xe2x80x9d bit and a xe2x80x9c0xe2x80x9d bit. In addition, a clock must be generated to differentiate bit positions.
In transmission, a signal can undergo several stages of amplification, attenuation, and limiting. Further, the transmission medium may act to degrade the signal. To recover the signal at a receiver, the signal voltage swing is analyzed around a threshold voltage. Signals above the threshold can be considered a xe2x80x9c1xe2x80x9d bit, while signals below the threshold can be considered a xe2x80x9c0xe2x80x9d bit. If the threshold is set correctly, no bits are misinterpreted in the threshold analysis. However, if the threshold is set incorrectly, then errors will result as the signal is converted into digital information. It is well known to control amplifier gain, loop gain, bandwidth, or receiver sensitivity in response to predetermined analog thresholds for improved performance. However, these analog system adjustments are not directly responsive to errors in converting the signal to digital information. That is, most systems attempt to simply adjust the aggregate power of the signal to a fixed level regardless of whether the majority of the power is noise.
Some forms of digital communications include forward error correction (FEC) information included as overhead. Using the FEC information, degraded or misinterpreted bits can be recovered. However, there is no standard practice for adjusting a receiver""s gain based on the number of corrected bit errors in a FEC encoded channel.
It would be advantageous if digital processing information could be used to improve the performance of an analog receiver.
It would be advantageous if the FEC correction information from a digital signal could be used for optimizing receiver parameters, such as gain, sensitivity, bandwidth, or bandwidth response.
It would be advantageous if the corrections performed in the FEC process could be applied in an analog receiver feedback circuit to minimize the number of corrections required.
Accordingly, this invention provides a process for adjusting the signal strength of an incoming FEC coded signal based on the decoded bit error rate. An FEC device is described with programmable features that enable a feedback network to optimize receiver performance by counting the difference between the number of xe2x80x9c1 to 0xe2x80x9d errors and xe2x80x9c0 to 1xe2x80x9d errors. The FEC feedback receiver performs as follows:
adjusting the receiver gain or thresholding based on decoded bit error rate;
providing a programmable loop response (bandwidth control); and
providing invertable error balance polarity.
The invention relies upon the random, but statistically evenly distributed, properties of the bit errors in the received signal to adjust the receiving process, i.e., adjust the gain of the receiver""s signal amplifier. In this manner, the receiver selects the optimal analog signal with respect to bit error rates, instead of using an absolute or predetermined signal level, which merely assumes an optimal receiving state.